Industry Segments - Schedule of Industry Segments and Eliminations (Details) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) site	Sep. 30, 2019 USD ($)
Segment Information
Number of operating segments | site					3
Net sales	$ 4,108			$ 5,859	$ 13,649	$ 14,283
Income (loss) from continuing operations before income taxes	(4,058)			(574)	(14,280)	1,223
Income tax benefit (expense)	403			(163)	1,896	(694)
Income (loss) from continuing operations	(3,655)			(737)	(12,384)	529
Asset impairments		$ 8,600
Gain on derivative instrument	88			(33)	(573)	(33)
Goodwill impairment			$ 1,200
Anadarko acquisition-related costs	5			924	302	974
Operating Segments
Segment Information
Valuation allowance on tax assets	37				37
Operating Segments | Oil and Gas
Segment Information
Net sales	2,989			3,993	10,089	9,062
Income (loss) from continuing operations before income taxes	(1,072)			268	(8,570)	1,478
Income tax benefit (expense)	0			0	0	0
Income (loss) from continuing operations	(1,072)			268	(8,570)	1,478
Net asset sale losses	795				795
Asset impairments					7,000
Gain on derivative instrument					1,100
Operating Segments | Chemical
Segment Information
Net sales	937			1,071	2,745	3,128
Income (loss) from continuing operations before income taxes	178			207	472	680
Income tax benefit (expense)	0			0	0	0
Income (loss) from continuing operations	178			207	472	680
Operating Segments | Midstream And Marketing
Segment Information
Net sales	364			1,163	1,358	2,888
Income (loss) from continuing operations before income taxes	(2,791)			400	(4,085)	1,010
Income tax benefit (expense)	0			0	0	0
Income (loss) from continuing operations	(2,791)			400	(4,085)	1,010
Impairment of equity method investment	2,700				2,700
Goodwill impairment					1,400
Corporate and Eliminations
Segment Information
Net sales	(182)			(368)	(543)	(795)
Income (loss) from continuing operations before income taxes	(373)			(1,449)	(2,097)	(1,945)
Income tax benefit (expense)	403			(163)	1,896	(694)
Income (loss) from continuing operations	$ 30			$ (1,612)	(201)	$ (2,639)
Anadarko acquisition-related costs					302
Loss on interest rate swaps					$ 577